Frequently Asked Questions About Colorectal Cancer Screening
There has been a lot in the news lately about improved screening methods for colorectal cancer that may have people wondering what option is really the best way to screen for the disease. The American Society for Gastrointestinal Endoscopy (ASGE), a group of 10,000 physicians worldwide dedicated to advancing patient care and digestive health, encourages people to speak with their doctor about which colorectal cancer screening method is best for them, as many factors play into which screening option is right for each patient.
All men and women over the age of 50 should be routinely screened for colorectal cancer. Colorectal cancer is a preventable and highly treatable cancer when caught at an early stage. Routine screening can save lives. To assist the public in understanding the different screening options available, the ASGE has developed a list of frequently asked questions about colorectal cancer and screening methods.
What is colorectal cancer?
Colorectal cancer (CRC), also known as colon cancer, is cancer that develops in the colon (large bowel) or the rectum and usually develops slowly over a period of many years. Before a true cancer develops, it usually begins as a non-cancerous polyp, which may eventually change into cancer. A polyp is a growth of tissue that develops on the lining of the colon or rectum. Certain kinds of polyps, called adenomas, are most likely to become cancerous. The only screening method that allows for the removal of polyps BEFORE cancer develops is colonoscopy.
Who gets colorectal cancer?
Anyone can get colorectal cancer. CRC is the third most commonly diagnosed cancer and the second most common cause of cancer death in the United States, with over 150,000 new cases diagnosed each year. More than 50,000 people die from it annually. Although colorectal cancer can strike at any age, 91 percent of new cases and 94 percent of deaths occur in individuals older than 50. The incidence rate of colorectal cancer is more than 50 times higher in people aged 60-79 than in those younger than 40.
What are the symptoms of colorectal cancer?
Although colorectal cancer often has no symptoms, warning signs that may indicate colon cancer include blood in your stools, narrower than normal stools, unexplained abdominal pain, unexplained change in bowel habits, unexplained anemia, and unexplained weight loss. These symptoms may be caused by other benign diseases such as hemorrhoids, inflammation in the colon or irritable bowel syndrome. However, if you have any of these symptoms, you should be evaluated by your doctor.
Why is screening for colorectal cancer important?
Colorectal cancer screening saves lives in two important ways:
- By finding and removing precancerous polyps before they become cancerous
- By detecting the cancer early when it is most treatable
Both men and women should undergo testing for the disease beginning at age 50. People with a high risk for CRC and those with a family history should talk with their doctor about being screened at an earlier age. A study by leading cancer groups found that colorectal cancer deaths have declined nearly five percent (2002-2004), in part due to prevention through screening and the removal of precancerous polyps.
What are the screening tests for colorectal cancer?
Screening is done on individuals who do not necessarily have any signs or symptoms that may indicate cancer. If symptoms exist, then diagnostic workups are done rather than screening. These are the tests recommended for colorectal cancer screening and some general pros and cons for each:
Stool blood test (fecal occult blood test--FOBT):
This test is used to find small amounts of hidden (occult) blood in the stool. A sample of stool is tested for traces of blood. People having this test will receive a kit with instructions that explain how to take stool samples at home. The kit is then sent to a lab for testing. If the test is positive, further tests will be done to pinpoint the exact cause of the bleeding. A rectal exam in the doctor’s office may examine for occult blood, but this is NOT considered adequate for colorectal cancer screening. The test should only be done with a take-home kit.
A newer kind of stool blood test is known as FIT (fecal immunochemical test). It is like the FOBT, perhaps even easier to do, and it gives fewer false positive results.
- Done at home
- Must be done yearly
- Least effective means of detecting cancer
- Viewed as unsanitary by some
- Patient must retrieve samples of stool in the toilet bowl
- All positive results MUST BE EVALUATED WITH A COLONOSCOPY
Flexible sigmoidoscopy (flex-sig):
A sigmoidoscope is a slender, lighted tube about the thickness of a finger. It is placed into the lower part of the colon through the rectum. This allows the physician to look at the inside of the rectum and lower part of the colon for cancer or polyps. This exam only evaluates about one third of the colon. The test is often done without any sedation, so it can be uncomfortable, but it should not be painful. Before the test, you will need to take an enema or other prep to clean out the lower colon.
- Does not require a vigorous bowel prep
- Does not require sedation
- Can only examine the lower third of the colon, the other two-thirds of the colon are not examined
- If polyps are found, the patient MUST RETURN FOR A FULL COLONOSCOPY
Colonoscopy allows for a complete evaluation of the colon and removal of potentially precancerous polyps. It is the only CRC screening tool that is both diagnostic and therapeutic. A complete bowel cleansing is required before the exam. The procedure uses a colonoscope, a tube with a light and video camera on the end, which allows the doctor to see the entire colon. If a polyp is found, the doctor can remove it immediately. The polyp is usually removed with small biopsy forceps or loop of wire (snare) that is advanced within a channel in the colonoscope. The polyp is then sent to the pathology lab for analysis. If anything else looks abnormal, a biopsy might be done. To do this, biopsy forceps are placed in the colonoscope and a small piece of tissue is removed. The tissue is sent to the lab for evaluation. This test is generally done with sedation and is well-tolerated. You will be given medicine that is injected through a vein to make you feel relaxed and sleepy.
- Examines the entire colon, making this the most thorough method for evaluating the colon and rectum
- High detection rate for polyps, including small polyps, and ability to remove them immediately during the procedure
- Done with intravenous sedation to assure comfort during the exam
- Given the “Gold Standard” rating above all other screening options by: American Society for Gastrointestinal Endoscopy (ASGE), American Gastroenterological Association (AGA), American College of Gastroenterology (ACG), the American Cancer Society (ACS), and the American College of Obstetricians and Gynecologists (ACOG).
- Small risk of puncture of the colon and bleeding
- Requires a complete bowel prep the night before to cleanse the colon
Barium enema with air contrast:
A chalky substance, which shows up on X-ray, is given as an enema. Air is then pumped into the colon causing it to expand. This allows X-ray films to take pictures of the colon. Laxatives must be used the night before the exam to clean the colon.
- Done without sedation
- Very low risk
- Uses X-ray radiation
- Can miss larger polyps and growths (over 50 percent polyps ³ 1 cm, and 15 percent of cancers)
- If polyps are found, the patient MUST BE FOLLOWED UP WITH A COLONOSCOPY
CT COLONOGRAPHY (also referred to as virtual colonoscopy)
A small tube is placed in the rectum and air is pumped into the colon to inflate the bowel. Then a special CT scan is used to image the colon. Recent studies show that it is effective in identifying medium to large polyps, but is ineffective in identifying small polyps. CT colonography may be best for low risk patients who cannot undergo or who failed a conventional colonoscopy. The same bowel prep as conventional colonoscopy is required and it does not use sedation.
- Examines the entire colon
- High detection rate for medium to large polyps
- Low risk
- Air distention of the bowel can be uncomfortable
- Ineffective in detection of small polyps
- Uses X-ray radiation
- If polyps or other abnormalities are found, A COLONOSCOPY MUST BE PERFORMED
- Is not covered by Medicare as an initial screening test
- Is not recommended by ASGE screening guidelines
For people eligible for Medicare, this is what is covered:
- Stool blood test (FOBT or FIT) each year for those 50 and over
- Flexible sigmoidoscopy (flex-sig) every 4 years for those 50 and over at average risk
- Colonoscopy every 2 years for those at high risk
- Colonoscopy once every 10 years for those 65 and over at average risk
- Barium enema with air contrast instead if a doctor believes that it is as good as or better than flex-sig or colonoscopy.
- Virtual colonoscopy is not covered by Medicare as an initial screening test.
The ASGE recommends talking to your doctor about screening options. If you are looking for a qualified physician in your area, please log on to www.screen4coloncancer.org or www.asge.org and click on “Find a Doctor.”